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Post Info TOPIC: Wasted solar when driving - solved
OKA


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Wasted solar when driving - solved
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My 2 Enerdrive 40A MPPT chargers are each connected to their own solar panel string.

I did this because the panels are of different vintages/brands and keeping them seperate gives best efficiency.

They can be connected as a single string and possibly lose 10-15% of their power but I chose not to.

However the Enerdrive selects "alternator" as the charge source when driving.

Meaning the solar panels output is 100% wasted as they're not selected.

To counter this I've knocked up a solution using a pair of DPDT 30A 12V relays and a cheapo 40A MPPT charger.

It works as described in the blurb attached.

Posting in case anyone else wants to use their solar when driving and their charger does not allow it.

 



Attachments
SOLAR SWITCH.pdf (147.6 kb)
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Mike Harding


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Good idea in principle but be mindful of two points:

With the alternator running too be cautious of exceeding the maximum battery charge current.

Switching DC is very hard on contracts ensure your relays are rated to 30A or as appropriate.



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OKA


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Yes Mike we're good on both points - D



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Cupie


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I just use the low-tech solution of connecting the Alternator output using Andersen Plugs, straight to my 3way fridge switched to 12v.

It has never worked as well. 

The Solar remains connected to the DC DC Charger & house battery. 

I do have the alternate option of plugging the Alternator into the DC DC charger if necessary, but then I have no 12v fridge connection.  I could use the fridge on Gas but people say that's a no no while traveling!

 



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OKA


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Yes, I'm not at all suggesting mine is superior. Far from it!

 

If I'd paid more attention when selecting the Enerdrives I might have found something that could draw from Panels and Alternators at the same time.

 

So it's a bit of a work-around :(

 

 



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Tony Bev


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Hi OKA

That is a good idea, so thanks for that information

I have a Renogy DC/DC 12V 50Amp Battery Charger with MPPT

It prioritises the solar panels to charge the house batteries first, saving some wear and tear of the alternator

If the battery is so run down that it requires the full 50 amps of charging, it will take power from both solar and alternator

As I normally do long road trips, (you have to from the west coast), I have a manual circuit breaker between the alternator and Renogy charger, which I switch off
This gives me peace of mind, that the house section is completely isolated from the engine battery, as 500 Watt of roof solar is more than I need for my 12 VDC compressor fridge

As I also normally have my motorhome laid up for long periods of time, I have another manual circuit breaker between the solar and Renogy charger
I find with lithium batteries (when parked up), I just switch the solar on for one day each couple of months, then switch the solar off




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Whenarewethere


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You could feed the alternator into a 12 to 24 DC-DC converter, then into a MPPT & have a second identical model MPPT from the solar panels. Set the voltage for the MPPT from the alternator to a whisker below the solar panel MPPT voltage so it is charging first.



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Brenda and Alan


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This seems an overly complicated solution. Simply disconnect the alternator feed from the solar controller by means of a switch or relay when not needed. 

Alan



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Cupie


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Brenda and Alan wrote:

This seems an overly complicated solution. Simply disconnect the alternator feed from the solar controller by means of a switch or relay when not needed. 

Alan

 There are a lot of solutions available, some requiring physical intervention like mine.

I did what you suggest but rather than installing a switch and I did look briefly at a rotary switch that would do the job, because I had a few spare Anderson plugs I just used that option.

I have a mate who is heavily into electronics & I'm sure that he would have come up with a hi-tech solution.

In the end I suppose that we will each choose a solution that suits our situation.

 



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